Contact filtration of viscous lubricating oils for decolorization



C. F. TEARS CONTACT FLTRATION OF VISCOUS LUBRICATING OILS FOR DECOLORIZATION Filed may 25, 1934 CLAUDE TEARS INVENTOR BY ZX @www Patented Aug. 29, i939 2,171,377

`crux-,TED STATES PATENT oFFicE CONTACT FILTRATION-OF VISCOUS LUBRI- OATING OILS FOR DECOLORIZATION Claude F. Tears, Mountain Lakes, N. J., assignor to The Petroleum Processes Corporation, Wichita, Kans., a corporation of Kansas Application May 25, 1934, Serial No. 727,497

8 Claims. (Cl. 196-147) The present invention is a continuation-impart 10W temperatuies, so is particularly effective for of the Tears application Ser. No. 679,073 which Washing oil from the decolorizing clay. This has issued as Patent No. 2,067,802, January 12, means that oil losses with exhausted clay can be 1937 and relates to the decolorization of viscous practically ,eliminated and there are no oxidation `lubricating oils, particularly the contact iiltration losses. 5 ofviscous lubricating oils in `solutions of propane The extreme volatility of propane or the like, 01 other liquefied normally gaseous hydrocarbon makes it possible to completely remove the solvent under pressure sufficient to hold the solvent in by use of heat at low temperatures or simply by the liquid state. l reduction of pressure on the system and this also The general objects of this invention are to is a factor in elimination of solvent losses with 10 reduce installation .and operating. costs, solvent exhausted clay. The ability to strip this solvent and oil losses, to increase the throughput per from the oil at 10W temperatures also avoids delunit of filter area and to raise the production of eterious effects of `high temperature Vstripping on finished oil per unit of clay, thereby reducing the iinished oil.

cost of clay consumption. Other objects, advantages and features oi the 15 The usual methods of contact filtration of invention are setV forth or Will appear in the follubricating oils involve. heating and mixing of lowing specification, particularly by reference to iine clay and oil to high temperatures and filterthe accompanying drawing. ing out the clay in plate filter presses. In handling The drawing forming in effect part of the specihigh viscosity oils, it is necessary to decrease the iication illustrates one practical commercial em- 20 viscosity, so as to increase the activity or eect bodiment of the invention, but as the same is of the clay and thus increase the rate of filtration primarily for purposes of disclosure, it should be per unit of iilter area. This viscosity reduction understood that structure and steps may be modihas been accomplished by heating the oil to fied to suit particular requirements and circumtemperatures in the range of 450 F. to 650 F., stances, all within the true intent and broad 25 or by putting theoil into solution in Warm naphscope of the invention.

thav and riiltering the solution, the iilter cake The single view in the drawing is a flow sheet lnally being Washed Wlll Clean naphtha t0 lediagram illustrating operation of the invention. cover the Oil Content and the naphtha removed i As shown, the oil to be treated is taken from from the clay usually by blowing With a stream tank l, and Charged by pump 2, to an agitator 3, 30 0f Warm all. Y into which iine contact de'colorizing clay is intro- The naphtha used in such prior operations is duced at Y4|,- i not a particularly good solvent and its boiling This @u clay `mixture is warmed as by means renee is relatively high AS e' Consequence, the of a heating coil 5,\in the bottom of the agitator 011 m the filter 'Cake Was nevel' Completely re and agitation effected by amotor driven agitating 35 moved and the naphtha employed for Washing the device 5.

cake. Wes never Completely recovered by en' From the agitator,the oil-clay mixture is passed blowing. There have thus been costly losses of by pump 1 to a mixer 8 Propane or like 1ique boo andfsolvent' `th Ik u ned normally gaseous diluent is also delivered to 40 euse o propane or o er l e norme y ges. this mixer from pressure'storage tank 9, by pump ecus liquid hydrocarbons as a solvent for the oil m. through une H in accordance with this invention results in cer- :1.o insure .complte S01 uti on of the ou in the tgl, (rilrllllgs rlll'mraked advantages over the propane, theniixtureoioil, propane and clay is p f then brought up' toatemperature usually be- In the iirst place, because of the extremely low t 1250 F d 175 F in he t r l2 aft meh viscosity of propane, the viscosity of the oil solu- Ween en Y' e e er W tion is much lower than anaphtha solution itis cooled in Cooler I3' could be. This means increased activity of the The .heetngzend @901mg ,Opere'tlene are een clay and hence increased yield of oil per ton of ducted undelfpressure Sufeent te Ifemtefm the clay and with actual reduction of clay consump- Solvent inthe liquid Slate all the heallng tempela- 50 non. The 10W viscosity of the solution also iure employed, by regulation 0f back pressure means reduced pressure drop through a lter Valve I4, in the Charge line l5, leading t0 the cake, thus increasing the throughput per unit vof lllei. Y v y Y iilter area; The filter consistsof a shell I6, constructed for 5@ Propane is an excellent oil solvent at relatively pressure operationV and equipped with iilter ele- 55 ments I1, in the top section and a heating coil in the bottom of the same.

The oil-clay-propane mixture fills the pressure shell and the oil solution passes out through the valved filtrate lines I9, leaving the clay retained on the filter elements. As the :filter chamber and other parts of the apparatus are constructed for pressure operation, high filtration pressures may be maintained as required.

The clay filtered from the oil solution builds up lter cake on the filter elements with a portion of it dropping to the bottom of the filter chamber. That part which remains on the filter units may be removed by back washing these units with liquid propane through the line I I--2Il, connected With selective draw-oifs I9, or with propane gas through line 2|, cut into the line 20, and connected in the return to storage line 22-l ahead of the liquefying condenser 23.

The clay dropping to the bottom of the filter chamber may-be kept in suspension in the oilpropane solution by circulation from the bottom back to the middle of the filter chamber by means of a line 24, having a pump 25 therein. Thus the greatest decolorizing effect may be gotten out of all the clay.

The operation is continuous and it is contemplated that a plurality of lter chambers be provided with facilities for switching to a clean lter chamber when the lower section of a preceding filter chamberrhas become more or less filled with the separated clay.

In the diagram, only one filter chamber is illustrated and when this has become filled in the lower portion with separated clay, the charge is shut off or switched to a clean filter and the exhausted clay is then washed with clean liquid propane from pump I0, through line 26. This line is entered in the bottom of the filter chamber causing the wash solvent to pass up through the clay and out through the filter elements, thus removing the recoverable oil retained by the clay.

After vwashing the clayof the recoverable oil as described, the filter chamber may be vented by means of valve 21, in the line 28, extending to the suction side of the compressor 29, which latter compresses the gaseous propane to the condensing pressure at the cooling temperature of the condenser 23. The vented propane thus condensed to liquid formisreturned to the pressure storage tank 9, through line 22.

The clay may be completely dried by vapplication of heat through use of heating coil I 8, in the bottom of the filter chamber and through which hot oil or other convenient heating medium may be circulated. Y

As an alternative step, the major portion of the propane may be exhausted from the clay by reduced pressure distillation through line 28-30, direct vto the condenser 23, the heat required being supplied by heating coil I8. AfterV distilling 01T most of the propane in this Way, the filter chamber may be vented to the compressor suction for complete removal of propane and the drying of the clay.

After'drying, the clay may be cleaned and reactivated by washing it with a color removing solvent, such as trichlorethylene stored in tank 3l, and delivered to the bottom of the filter chamber by pump 32, through line 33-26. This color removing solvent passes out through the filter elements into the filtrate line 34, and is transferred by pump 35, through a branch line 36, to a recovery system including a distillation unit 31. The type'ofunit employed will depend upon'the solvent used. For trichlorethylene a low pressure distillation system is employed. In this unit, the color removing solvent is distilled overhead from the color containing residue as by application of heat through a heating coil 38, in the bottom of the still. The vapor passing out overhead through line 39, is condensed by condenser 40, and returned in the liquid phase to the color removing solvent storage tank 3I, and the color bearing residue is removed from the bottom of the still through a cooler 4 I.

The color removing solvent remaining in the chamber after the washing described may be removed from the clay in the same manner as rst described for removal of propane, that'I is, by venting through line 30, and the use of heat at I8, and suction through line 28, condensing at 23, and returning in liquid phase through line 22-42 to storage at 3|.

The reactivated clay after being dried can be removed from the filter chamber through the clay discharge connection 43, at the bottom of the chamber and be returned to the agitator for reuse.

The ltered oil taken off by the line 34 is chargedby pump 35, to a pressure distillation still or stabilizer 44, where the propane is driven off from the oil by application of heat through heating coil 45, or the like. The vaporized propane passing off overhead through line 46, is condensed in the condenser 41, and returns through this line to the pressure storage tank 9. The liquid propane used for Washing oil from the clay is also recovered in this same system and by similar procedure.

The decolorized filtered oil With the major portion of the propane removed Hows from the bottom of the stabilizer through line 48, to a low pressure stripper 49, where the last traces of propane are removed through the vapor line 50, connected with the suction side of the compressor.

The nished oil passes off from the bottom of the stripper through line 5I and cooler 52, to storage.

While usually the decolorizing clay may be g first mixed with the oil, in some instances, the clay may enter the system with the propane or be mixed with the oil-propane solution.

The structure of the filter may vary. Simple fabric filter leaves or edge type elements as in the Hele-Shaw or Cuno filter units may be used in a pressure lter chamber as described. Also a continuous rotary type filter equipped with cake Washing facilities and automatic mechanical cake removal map be employed. A simple pressure f plate filter of the closed type similar to those used in conventional contact filtration also may be employed.

With pressure filter chamber operation as described, it is possible to operate the filter chamber at a pressure sufficiently high to effect delivery of the ltrate direct to the pressure stabilizer without using a stabilizer charging pump, such as indicated at 35.

While the color removing solvent operation is a desirable feature of the process, it is not essential to the rest of the operation. This reactivating treatment is a desirable adjunct and may or may not be used with the contact filtration in propane solution, as circumstances make advisable.

The process is continuous in the sense that no temperature and reaction periods are required as in processes heretofore proposed. There are therefore practically no losses in time or materials and superior results are attained economically.

What is claimed is:

1. The herein disclosed process of treating lubricating oil, which comprises dissolving lubricating oil in a liquefied normally gaseous hydrocarbon solvent under pressure suflicient to maintain the solvent in the liquid state, heating and contacting the solution with adsorbent clay at a temperature in excess of F. under pressure sufficient to maintain the heated solvent in the liquid state, separating the solution from the clay under pressure suicient to maintain the solvent in the liquid state and separating the treated oil from the solvent.

2. The process of claim 1, in which the solvent is liquefied propane.

3. The process of claim 1, in which the contacting is effected at a temperature within the range of 125 F. to 175 F.

4. The process of claim 1, With the added steps of washing retained oil from the adsorbent clay with fresh solvent under pressure sufficient to maintain the solvent in the liquid state, heating the clay to distill retained solvent from it under superatmospheric pressure, reducing the pressure on the heated clay to vaporize remaining traces of solvent from the clay and returning the solvent in liquefied state into mixture with fresh lubricating oil being treated as described.

5. The process of decolorizing lubricating oil, Which comprises dissolving lubricating oil in liquefied normally gaseous hydrocarbon solvent under pressure sufcient to maintain the solvent in the liquid state, mixing ne contact clay with the solution under such pressure, heating the solution to a temperature in excess of 125 F. under pressure suflicient to maintain the solvent in the liquid state, filtering the Contact clay from the solution under pressure suicient to maintain the solvent in the liquid state and separating the solvent from the treated oil.

6. The process of claim 5, in which the heated solution is cooled before filtering.

7. The method of continuously decolorizing viscous lubricating oil by contacting, which comprises mixing the oil to be decolorized with a comminuted absorbent decolorizing clay and then continuously mixing said mixture under pressure with a normally gaseous liquefied hydrocarbon solvent to effect extreme dilution of the oil in the solvent, passing the mixture of oil, decolorizing clay and solvent continuously through a heating Zone at a temperature of 125 F. to 175 F. to effect complete solution of the oil and contact decolorization in transit under pressure sufficient to hold the solvent in the liquid state and thence in continuous flow through a cooling Zone to remove added heat and then filtering the cooled mixture under pressure.

8. The method of continuously decolorizing viscous lubricating oil by contacting, which comprises mixing the oil to be decolorized with a comminuted adsorbent decolorizing clay and then continuously mixing said mixture under pressure qwith a normally gaseous liquefied hydrocarbon solvent to effect extreme dilution of the oil in the solvent, passing the mixture of oil, deco-lorizing clay and solvent continuously through a heating zone at a temperature of 125 F. to 175 F, to effect complete solution of the oil and contact decolorization in transit under pressure sucient to hold the solvent in the liquid state and thence in continuous flow through a cooling zone to remove added heat and then filtering the cooled mixture under pressure, relieving pressure on the filter to vaporize the solvent from the adsorbent decolorizing clay, liquefying the solvent and recycling it for decolorizing additional lubricating oil.

CLAUDE F. TEARS. 

